Problem: Express this product in scientific notation: $(6.40\times 10^{4})\times (9.00\times 10^{5})$
Start by collecting like terms together. $= (6.40\times 9.00) \times (10^{4}\times 10^{5})$ When multiplying exponents with the same base, add the powers together. $= 57.6 \times 10^{4\,+\,5}$ $= 57.6 \times 10^{9}$ To write the answer correctly in scientific notation, the first number needs to be between $1$ and $10$ . In this case, we need to move the decimal one position to the left without changing the value of our answer. $ $ We can use the fact that $57.6$ is the same as $5.760 \times 10$ $ = {5.760 \times 10} \times 10^{9} $ $= 5.760\times 10^{10}$